Arsenate of lead



-Reissued Apr. 20, 1926.

UNITED STATES,

I Re. -l6,33l- PATENT OFFICE.

H ABBY B. GOODWIN, OE GRAND JUNCTION, COLORADO, ASSIGNOR TO THE LATIMER cnnurcancourm, A CORPORATION or coLonAno'J ARSENATE 0! LEAD.

Bo Drawing. Original No. 1,322,008, dated November 18, 1919, Serial No. 248,343, filed August 5, 1918.

Arsenate of lead is'used generally for the killing or elimination of various insects enemies to various forms of vegetation and finds a large use to this end in orchards. It has now become a common practice to spray arsenate of lead onto fruit trees which, with-.

out some treatment, may be subject to an injurious attack by various insects. The insects commonly attack both the leaf and the fruit. They are sometimes very small, being almost invisible to the naked eye, and it is nearly impossible to locate them on the trees.

It becomes necessary therefore, to cover both the trees and their foliage with some material poisonous to the insects.- Arsenate of lead is 'generall admitted to be very ellicient for this en and it is commonly used by orchard owners and recommended by scien- Arsenate of'lead is oiferedcommercially in two forms, paste and powdered. While sults from the arsenate of lead treatment it is the paste form has been found (efficient as an insecticide, it is diflicult to produce a product in the paste form that will stay uniform until it is used. Arsenate of lead in the powdered form is, therefore, being more generally used.

When used for sprayingfruit trees 1 pound ofwarsenate of'lead powder is gener-' The ally added to gallons of water. arsenate of lead does not dissolve in the water but is held in suspension in it and the physical mixture of water-and arsenate of lead is then passed through sp'raying aprparatus' and so distributed on the trees.

The Water evaporates leaving the arsenate' of lead adhering to the trees where 'it may be found and consumed by the insects .to be destroyed. In order to get satisfactory renecessary to have the poison thoroughly distributed overthe trees. So that the poison my be readily available to the insect it should in very fine articles onthe trees. It willbe apprehende that in order to get I the arsenate of lead thoroughly distributed on the trees it is necessary to have it more Application for reissue filed November 8, 1921. Serial No. 513,847.

or less uniformly suspended in the-water in the spraying tank-and in thewater asit is delivered by the spray to the trees. It is the desire of thejmanufacturer of arsenate of lead, therefore, to produce a product which may readily be suspended in water and which when mixed with water, will remain in suspension. To this end mucheffort has been'devoted to producing arsenate of lead in a fine impalpable powder. To a limited degree these efforts have been succce ssful and there are on the market powdered arsenates of lead which may be added to water and by agitation thoroughly mixed and gotten in suspension. Prior to my invention therehas been no arsenate of lead which would remain in suspension for long under commercial conditions or in the proportions usually employed for spraying.

It is the object of my invention to provide an arsenate of lead composition which will not only readily become suspended in water but will remain suspended in the water for a considerable period of time under ordinary conditions and when added to water in the proportions generally adopted for spraymg.

mixed therein in such a way that the arsenate of lead becomes evenly and uniformly suspended throughout the water.

A settling test commonly employed by manufacturers and in laboratories is to add 15 grams of dry. material to 250 cubic centimeters of water aiid after properly agitating to get all the material in suspension in the Water, tolet'rest quiet and then measure the amount of clear' 'water at the top of the While not necessarily confined to such column at the end of five minutes, and again at the end of ten minutes. This is a convenient and easy test but it does not siniu- .late practical conditions for the reason that senate of lead mixture is only 1 pound of powder to 50 gallons of water. Moreover, the clear water proportion in the top of the scale is not of as much importance as thegeneral distribution of material throughout the body of liquid. For instance it may happen that only 5 per cent of liquid will be clear whereas 60 per cent or 75 per cent of the material may have already settled to the bottom per cent of the liquid leaving only a small proportion of the material distributed throughout the liquid.

In order, therefore, to determine the conditlon e ristin'g under circumstances such as are met 1n practical use of arsenate of lead as an insecticide, I have made a test by mixing a sample of arsenate of lead in the proportlon of 1 pound of the powder arse- 'nate of lead to gallons of water. After thoroughly mixing, agitating, and getting substantially all of the arsenate of lead in suspension in thewater, it was allowed to remain quiet for five minutes at the end of which time the upper half of the liquid and the arsenate of lead suspended therein wassiphoned off from the top of the vessel into a weighed d sh. The liquid so siphoned off was then evaporatedfto-dryness and the residu e weighed. One half of'the weight of the entire quantity of arsenate of lead suspended orlgmally was then divided into the weight of the dried residue remaining in the dish. Thls gives the per cent of arsenate of lead remaining in suspension in the upper half of the liquid. By repeatin the test and lettlng the mixture rest quiet or longer periods it is possible to obtain information of prac-. tical value concerning the continuance of suspensibility of the arsenate of lead in water, 4 I

In the particular sample tested I find that there still remained in suspension in the .upper half of the fluid at the end of 5 minutes 31.91 per cent of the arsenate of lead. At the end of 10 minutes there remained suspended in the upper half only 10.04 per cent. At the end of 20 minutes there remained suspended 8.25 per cent. At the end of 40minutes 6.16 per cent. At the end of minutes 1.87 per cent. The same material when tested by the ordina method of adding 15 grams to 250 cubic centimeters of water showed at the end of 5 minutes only 2 cubic centimeters of clear water and at the end of 10 minutes only 4 cubic centimeters of clear water which figures indicate that,

I according to the ordinaryjmethod of testing,

it is a indeed it is roduct of very high qualit and the best product I can nd' on the market. A

I find that if I add to the arsenate of lead used in the above'test a quantity of commercial tannin I obtain a much superior suspensibility. The tannj'nwhich I have used is the browntpowderof commerce produced with less than of 1 per cent and again with as much as 10 per cent or more I find however, that a mixture of of 1 percent of tannin is suflicient for practical purposes and has no ill effect on the insecticidal properties of theiarsenate of lead. On adding this mixture of arsenate of lead and of 1 per cent of tannin to water in the orchard proportions of 1 pound to 50 gallons I find that after shaking thoroughly and mixing them and then leaving still for 5 minutes and siphoning off the upper half of the liquid and its contents asin the last test,

there remained suspended 88.93 per cent'as I against 31.91 per cent when tannin was not used. At the end of 10 minutes there was; suspended 84.45 per cent as against 10.04

per cent when tannin was not used. At the end of 20 minutes 81.08 per cent. At the end of 40 minutes 74.7 5 per cent. At the end of 80 minutes 62.67 per cent. At the end of 140 minutes 47 .70 per cent. At the end of 200 minutes 41.7 5 per cent as against 1.13 per cent at the end of 200 minutes when no tannin was used.

The value of the comparative settling tests as outlined above is that they offer simple means of determining the physical qualities or fitness of the material.

The active principle of tannin is tannic- Since suspensibility generally is a furictionf fineness I believe that the added tanni causes the arsenate of lead to become or remain in every finely divided state which also'causes it to have an increased covering capacity on the tree thus effecting a marked economy in the quantity needed for an orchard but I am not sure of this 1 invention does not depend action of the "tannin or added tothe arsenate of theory and In thereon. Suc tannic acid when lead is obviously that of a protective colloid. for the particles of said insecticide. .The.

use of such protective colloids in other connections is admittedly well ,known, but I believe it to be new to ap ly same to: the; specific field in hand. As .i lustratedjin the case of the ingredients just named as being added by metothearseuate of lead, such of water falling in the form of rain to a protective colloid must be chemically inert relatively to such arsenate. Tannin and tannic acid are also of course of organic origin.

Assuming, however, the correctness of-the foregoing theory, they action of the small percentage of tannin is that of a deflocculating agent, the use of which in this particular connection I believe to be origlnal' with me and entirel unique. I

As a corollary to such increased ensibility, due to the very finely divided state in which the ar -senate of lead is caused to form andis maintained by the addition of such deflocculating agent, not only are the spreading and covering qualities of the lead arsenate im roved when applied to foliage but, after (i heretofore in a form in which the particles tend to agglomerate, thus resulting in anuneven distribution upon being spra In other words, when such finely divided uniformly distributed product is dried it forms a continuous film that is naturally 'more adherent to the surface to which it is applied and will resist the erosive action markedl greater degree.

In or er to achieve benefits by the use of my invention it is not necessary that the arsenate of lead to which the tannin is added be chemically pure as various impurities ma be presentin small or minute quantities wit out materially diminishing the'efi'e'ct of the tannin. v

I find, however, that if there be present in the arsenate of, lead a small quantity of litharge "or of acetate of lead the increased suspensibility otherwise produced by tannin is not obtained. Minute quantities of litharge present" do not aifect the result. For instance, in a sample of arsenate of lead in which there was present one tenth of 1 per cent of litharge substantially as good results were obtained by the addition of of 1 er cent of tannin as if the litharge ha not been present. With a sample of arsenate of lead in whichthere was present one tenth of 1 per cent of lead acetate substantially as good results were obtained by the addition of of 1 per cent of tannin. as if the acetate of lead had not been present. However, a sample of ar- =senate of lead containing a proximately 1 per cent of litharge was su tantially unafl'ected as to. its capacity for remaining suspendediwwater by the addition of of 1 percent of tannin. Likewise a sample containing approximately 1 per cent of lead.

free litharge or free lead acetate the fin-f rying, such arsenate is not as readily washed off as when prepared as Numerous other changes,

, acetate, and tannin.

of these sa ts. I find, therefore, that some of the arsenates of leadon the market do not lend themselves, because of the impurities contained, to the production of the beneficial results to be obtained by the addition of tannin to pure -arsen ate of lead.

My invention is not confined in its appli cation to powder arsenate of lead nor to that made by the process set out above for, by whatever processit is made, if it is properly and sufliciently purified, it will lend itself to my discovery and more especially so if it-is reduced.t0.,fine,s0ft particles before tannin is added. .f v

I- find it convenient to add the dry powdered tannin or tannic acid to the prepared powdered arsenate of lead but it may be arsenate of lead at some intermediate sta e in the'procew of manufacture" or even sub sequent to .its mixture with they water. variations and deviations from the detalls set out above may be resorted to without departing from my invention.

I claim as my invention: 1. A mixturc of arsenate of lead containing less than one per cent offree litharge,

and tannin. I Q

2. A mixture of arsenate of lead containing less than one per :cent of free lead 3. A mixture of arsenate'oflead, and one- 5. The method of increasing the persistence of suspensibility of: arsenate of lead in water consisting in adding ondfqhalf of' ere arsena'te one per cent of tannin to pow of lead;

6. 1%16 method of increasing-the persistence o suspensibility in water of arsenate of lead, consisting in mixing tannin'there-l with in .the wdrypovvdered form.

7. A mixture of, tannin and the precipitate formed by mixingv lead acetateand arsenic acid.

8. An insectitude of which the principal,

active ingredient is 'arsenate 'of lead with less'than one per cent of free lead acetateins-Q and less than one per cent of free litharge' and more than three tenths ofone percent of tannic acid. I f 1 v 9. A mixture of dry, soft, bulkyfpowdered arsenateof lead, and approximately one ha f of one per cent of tannin by weight.

10. An insectitude composition comprising lead--arsenate and I a deflocculating agent,

'said composition -b'eing readily suspendable' in water for spraying and having improved spreading and 'overing qualities 'vvhen thus applied, and forming an adherent dry film resistant to the erosive action of water.

11. An insecticide composition comprising lead arsenate and a deflocculating agent intermixed herewith, the percentage of said agent being relatively small.

12. An insecticide composition comprising lead arsenate and a deflocculating agent intermixed therewith, the amount of said agent being lessf'tha'n '10 per cent of the. amount of arse'nate' of lead in the mixture.

13. The herein'described product comprising lead 'arsenate particles intimately associated with a colloid of organic origin.

14. The herein described product consisting of a water-insoluble"insectitude ma terial and incorporated therewith, a relativelysmall quantity of an organic subprecipitate stance capable of serving as a protective colloid for the particles of said insecticide.

1 5. A lead arsenate insecticide having the particles thereof coated with an organic ro- 'tective colloid, the amount of said col oid HARRY B. GOODWIN. 

